Spinal cord injury is an important clinical problem in the United States with severe injuries leading to major permanent disability and often death. Treatment of the cord lesion has been extremely difficult, in part due to the impossibility of determining the nature and magnitude of structural damage (specifically hemorrhage, edema, necrosis, and cavitation) which has occurred and similar limitations in our ability to follow the change in the extent of these lesions in response to therapy. Magnetic resonance (MR) imaging holds promise for addressing these problems. MR is noninvasive and has been shown to provide tissue characterization not obtainable in any other manner. This investigation will evaluate the utility of MR in acute and chronic spinal cord injury by answering the following questions: 1. Does magnetic resonance (MR) accurately display the major pathologic features (hemorrhage and edema) of acute spinal cord injury? 2. Does the extent of hemorrhage and edema as displayed on MR images in the acute stage correlate with the severity of trauma administered? 3. Does the extent of hemorrhage and edema as displayed on MR images in the acute stage correlate with the functional outcome of the injury? 4. Do changes in the extent of edema over time as displayed by MR reflect functionally significant changes in the evolving lesion? This study will be conducted by subjecting Sprague-Dawley rats to weight drop thoracic spinal cord injury and imaging by MR at 4 hours to 28 days after trauma. The extent of hemorrhage, edema, necrosis, and cavitation as displayed by MR will be measured and the MR findings will be correlated with quantitative histologic examination and serial assessment of hind limb function.